fix(assert): Validate delimited defaults

Fixes #3514

src/build/arg.rs

@@ -4633,6 +4633,12 @@ impl<'help> Arg<'help> {
         self.num_vals
     }
 
+    /// Get the delimiter between multiple values
+    #[inline]
+    pub fn get_value_delimiter(&self) -> Option<char> {
+        self.val_delim
+    }
+
     /// Get the index of this argument, if any
     #[inline]
     pub fn get_index(&self) -> Option<usize> {

src/build/debug_asserts.rs

@@ -1,5 +1,7 @@
 use std::cmp::Ordering;
 
+use os_str_bytes::RawOsStr;
+
 use crate::build::arg::ArgProvider;
 use crate::mkeymap::KeyType;
 use crate::util::Id;
@@ -686,7 +688,16 @@ fn assert_defaults<'d>(
 
             if let Some(validator) = arg.validator.as_ref() {
                 let mut validator = validator.lock().unwrap();
-                if let Err(err) = validator(default_s) {
+                if let Some(delim) = arg.get_value_delimiter() {
+                    for part in default_s.split(delim) {
+                        if let Err(err) = validator(part) {
+                            panic!(
+                                "Argument `{}`'s {}={} failed validation: {}",
+                                arg.name, field, part, err
+                            );
+                        }
+                    }
+                } else if let Err(err) = validator(default_s) {
                     panic!(
                         "Argument `{}`'s {}={} failed validation: {}",
                         arg.name, field, default_s, err
@@ -697,7 +708,17 @@ fn assert_defaults<'d>(
 
         if let Some(validator) = arg.validator_os.as_ref() {
             let mut validator = validator.lock().unwrap();
-            if let Err(err) = validator(default_os) {
+            if let Some(delim) = arg.get_value_delimiter() {
+                let default_os = RawOsStr::new(default_os);
+                for part in default_os.split(delim) {
+                    if let Err(err) = validator(&part.to_os_str()) {
+                        panic!(
+                            "Argument `{}`'s {}={:?} failed validation: {}",
+                            arg.name, field, part, err
+                        );
+                    }
+                }
+            } else if let Err(err) = validator(default_os) {
                 panic!(
                     "Argument `{}`'s {}={:?} failed validation: {}",
                     arg.name, field, default_os, err

tests/builder/default_vals.rs

@@ -648,15 +648,47 @@ fn default_values_are_possible_values() {
 
 #[cfg(debug_assertions)]
 #[test]
-#[should_panic = "Argument `arg`'s default_value=value failed validation: invalid digit found in string"]
-fn default_values_are_valid() {
+#[should_panic = "Argument `arg`'s default_value=one failed validation: invalid digit found in string"]
+fn invalid_default_values() {
     use clap::{Arg, Command};
 
     let _ = Command::new("test")
         .arg(
             Arg::new("arg")
                 .validator(|val| val.parse::<u32>().map_err(|e| e.to_string()))
-                .default_value("value"),
+                .default_value("one"),
+        )
+        .try_get_matches();
+}
+
+#[test]
+fn valid_delimited_default_values() {
+    use clap::{Arg, Command};
+
+    let _ = Command::new("test")
+        .arg(
+            Arg::new("arg")
+                .validator(|val| val.parse::<u32>().map_err(|e| e.to_string()))
+                .use_value_delimiter(true)
+                .require_value_delimiter(true)
+                .default_value("1,2,3"),
+        )
+        .try_get_matches();
+}
+
+#[cfg(debug_assertions)]
+#[test]
+#[should_panic = "Argument `arg`'s default_value=one failed validation: invalid digit found in string"]
+fn invalid_delimited_default_values() {
+    use clap::{Arg, Command};
+
+    let _ = Command::new("test")
+        .arg(
+            Arg::new("arg")
+                .validator(|val| val.parse::<u32>().map_err(|e| e.to_string()))
+                .use_value_delimiter(true)
+                .require_value_delimiter(true)
+                .default_value("one,two"),
         )
         .try_get_matches();
 }